1. Field of the Invention
The present invention relates to a dynamic false contour reducing method, a dynamic false contour reducing circuit, a display device, and a program for displaying an image on a display based on display data.
2. Description of the Related Art
A display device displays an image based on an input signal (display data) on a display part. The input signal is a signal for displaying an image at a pixel Pi,j. As shown in FIG. 1, the display device is sequentially applied with input signals (display data) corresponding to a pixel Pi−4, a pixel Pi−3, a pixel Pi−2, a pixel Pi−1, a pixel Pi, a pixel Pi+1, a pixel Pi+2, a pixel Pi+3, where i is an arbitrary integer.
The display device can display a moving image in accordance with display data on the display. Here, each pixel is comprised of one subfield which has a first SF (subfield) to an eighth SF. A gradation level is set to each of the first SF to eighth SF of each pixel for indicating the depth of three colors, R (red), G (green), and B (blue). For example, when a gradation level representative of unlit state (black) is set to each of the first SF to eighth SF of a pixel Pi, the gradation level of the pixel Pi indicates zero. When a gradation level representative of lit state (other than black) is set to at least one of the first SF to eighth SF of the pixel Pi as a pixel of interest, the gradation level of the pixel Pi indicates a range from one to 255.
In the example shown in FIG. 1, a gradation level representative of lit state (white display in FIG. 1) is set to the first SF to seventh SF of the pixel Pi−4, pixel Pi−3, pixel Pi−2, and pixel Pi−1, while a gradation level representative of unlit state (black display in FIG. 1) is set to the eighth SF of the pixel Pi−4, pixel Pi−3, pixel Pi−2, and pixel Pi−1. The gradation level representative of unlit state (black display in FIG. 1) is set to the first SF to seventh SF of the pixel Pi, pixel Pi+1, pixel Pi+2, and pixel Pi+3, while the gradation level representative of lit state (white display in FIG. 1) is set to the eighth SF of the pixel Pi, pixel Pi+1, pixel Pi+2, and pixel Pi+3. When a moving image is displayed on the display part, display data is displayed at positions corresponding to the pixel Pi−4, pixel Pi−3, pixel Pi−2, and pixel Pi−1 of the display part in the order of the first SF to seventh SF (lit) and the eighth SF (unlit). Also, display data is displayed at positions corresponding to the pixel Pi, pixel Pi+1, pixel Pi+2, and pixel Pi+3 of the display part in the order of the first SF to seventh SF (unlit) and the eighth SF (lit).
When a user views a moving image displayed on the display part, a dynamic false contour 100 appears as shown in FIG. 1. The dynamic false contour is described in “All about Plasma Display” written by Heijyu Uchiike and Shigeo Mikoshiba, pp. 164-165, Kogyo Chosakai Publishing Inc., May 1, 1997. When the dynamic false contour 100 appears, a still image displayed on the display part is affected as well. It is desired to reduce the dynamic false contour 100.
There is known a driver for a selfluminous display panel which generates less dynamic false contours (see Japanese Patent Application kokai No. 9-102921 (Patent Document 1)). According to the technique described in Patent Document 1, for driving a selfluminous display panel in accordance with a subfield method to display an image in gradations, display data of the image is corrected based on false contours caused by the subfield method. The display panel driver described in Patent Document 1 is characterized by comprising determining means, and correction selecting means. The determining means determines the presence or absence of a false contour on a pixel-by-pixel basis based on fluctuations between frames for the same pixel and fluctuations between pixels for the same frame. The correction selecting means selectively corrects the display data in accordance with the result of the determination.
The false contours are not sufficiently reduced only by selectively correcting display data simply in accordance with the result of determination as to the presence or absence of a false contour, as is the case with the display panel driver described in Patent Document 1.
Japanese Patent Application Kokai No. 2002-229510 (Patent Document 2), for example, describes a prior art example which is made in view of the problem mentioned above. Patent Document 2 describes generating a plurality of candidate pixel signals for each pixel of interest, and selecting the candidate signal which exhibits the smallest magnitude of false contour of the plurality of candidate pixel signals for a display operation.
Other than Laid-open Japanese Patent Applications Nos. 9-102921 and 2002-229510, there is “All about Plasma Display,” written by Heijyu Uchiike and Shigeo Mikoshiba, pp. 164-165, Kogyo Chosakai Publishing Inc., May 1, 1997.